Mature - applied to cells and tissues that have differentiated into their final adult form assuming the function or form characteristic of cells or tissues found in a fully developed part of the plant.

Membrane - i. a thin pliable sheet of material that separates and forms the interface between two environments. ii. a thin flexible sheet of tissue connecting, covering, lining, or separating various parts or organs. iii. a thin (10 nm) structured bi-layer of phospholipid and protein molecules surrounding every biological cell and intracellular organelles such as chloroplasts,mitochondria and the cell nucleus. Functionally distinct proteins floating in the membranes of cells and organelles control the passage of substances into and out of the enclosed space, catalyse chemical reactions at the membrane surface and allow cell-cell recognition.

Mescal - a strong alcoholic liquor, similar to Tequilla, made by distillation of a fermented preparation of the starchy core of Agave angustifolia and other species. Also a common Mexican name for certain Agaves.

Mesembrine - a narcotic alkaloid found in Scletium tortuosum (kanna) and other species of Aizoaceae (Mesembryanthemaceae). Mesembrine inhibits serotonin uptake thus increasing extracellular levels of serotonin and therefore increasing serotonergic neurotransmission. Mesembrine is also an inhibitor of the enzyme phosphodiesterase. Mesembrine is certainly mood-altering and may be an anti-depressant.Structure of Mesembrine

Mitosis - the normal process of cell division when the diploid or other normal chromosome number is conserved to produce two daughter cells with identical numbers of chromosomes to the parent cell.

Mitochondria - a functional organelle in the cellcytoplasm, of both plants and animals, containing highly ordered membrane-bound arrays of enzymes and proteins involved in respiration and energy metabolism. Mitochondria contain a small circular piece of DNA, which carries genes for a small number of mitochondrial proteins. Mitochondria are inherited almost exclusively from the female parent, and DNA sequences encoding mitochondrial genes are analysed to determine inter-specific relationships and the slow rates of mutation in mitochondrial DNA sequences are used as one form of "molecular clock."

Monophyletic -
of a group of organisms sharing and including a common ancestor, and including all the descendents of that common ancestor, therefore with similar characteristsics. Otherwise known as a clade. See also: paraphyletic, polyphyletic.

Mycorrhiza - a symbiotic relationship between certain fungi and the roots of plants, including orchids and many types of tree. Mycorrhiza may be ectotrophic, where the fungal hyphae invades the host roots or endotrophic where the fungal hyphae are entirely within the root cells. The fungal hyphae can help the roots to absorb essential nutrients and in some species are essential to the normal growth of the plant.